Mercury distillation apparatus with electric heat control



June 6, 1967 MERCURY DISTILLATION APPARATUS WITH ELECTRIC HEAT CONTROLFiled Nov. 27, 1963 T VACUUM J. W. GRIFFITH ETAL 2 Sheets-Sheet 1 24 la8 32" I92; 2081' a/x x ea a Joseph WGri f F1 H1 Guni'her Weiss INVENTORSBY @QQQM r EYN b Q8 .1. 9% .3. 3w 3 H G 2 @MN fi N/Z vww 4 fi L www QM3N J. w. GRIFFITH ETAL 3 2 Sheets-Sheet 2 INVENTORS Joseph WGr' ffjfhGunf'her {4/6158 Hgen 1' June 6, 1967 MERCURY DISTILLATION APPARATUSWITH ELECTRIC HEAT CONTROL Filed Nov. 27 1963 3,324,009 MERCURYDISTILLATION APPARATUS WITH ELECTRIC HEAT CONTROL Joseph W. Griflith,Portland, and Gunther Weiss, Beaverton, reg., assignors to Electra GlassLaboratories, Inc., Beaverton, 0reg., a corporation of Oregon Filed Nov.27, 1963, Ser. No. 326,529 6 Claims. (Cl. 202173) This invention relatesto apparatus for distilling mercury, and more particularly to automaticapparatus for the continuous multiple distillation of mercury.

Apparatus provided heretofore for the continuous distillation of mercuryare characterized by being bulky assemblies which utilize an excessiveamount of space, which are difficult and time consuming to clean, andwhich utilize complex and costly control equipment while still providingonly minimum control.

Accordingly, it is the principal object of the present invention toprovide mercury distillation apparatus in the form of a compact assemblyof a minimum of components, utilizing a minimum of space, whileproviding for the eflicient production of mercury of high purity.

Another important object of this invention is the provision of mercurydistillation apparatus which is capable of being cleaned with speed andfacility, without disassembly.

Still another important object of the present invention is the provisionof mercury distillation apparatus in which operation is controlledautomatically in accordance with predetermined conditions of coolantcirculation and mercury levels.

A further important object of the present invention is the provision ofmercury distillation apparatus which includes simplified automatic feedcontrol means for maintaining precise mercury feed to the distillationcomponent.

A still further important object of this invention is to provide mercurydistillation apparatus which is of simplified construction foreconomical manufacture and requires a minimum of maintenance.

The foregoing and other objects and advantages of the present inventionwill appear from the following detailed description, taken in connectionwith the accompanying drawings in which:

FIG. 1 is a fragmentary schematic view in side elevation of mercurydistillation apparatus embodying the features of the present invention;

FIG. 2 is a fragmentary sectional view taken along the line 2--2 in FIG.1; and

FIG. 3 is a schematic electrical diagram of a control circuit for thedistillation apparatus of the present invention.

Referring primarily to FIG. 1 of the drawings, the preferred embodimentof the apparatus illustrated includes a supply reservoir from whichdirty mercury to be distilled is fed by gravity to an automaticallycontrolled constant level feed device 12. From this device the mercuryis fed to the first of three evacuated boilers 14, 16 and 18,respectively. The first boiler communicates with a condenser 14' havinga distillate outlet tube 20 communicating through the vapor trap 22 withthe second boiler 16. The second boiler communicates with a condenser16' Whose distillate outlet tube 24 communicates through the vapor trap26 to the third boiler 18. The third boiler communicates with thecondenser 18' whose distillate outlet tube 28 communicates through thevapor trap 30 with the upper end of a distillate receiver flask 32.

The receiver flask and the condensers are connected at their upper endsto a source of vacuum (not shown), and the boilers are connected attheir lower ends through valves to a drain tube, as explained more fullyhereinafter.

Considering the foregoing in greater detail, the supply United StatesPatent 0 3,324,009- Patented June 6, 1967 reservoir 10 comprises a tank34 provided with an inlet opening 36 (FIG. 3) for introducing dirtymercury to be distilled. The tank also is provided with an outlet tube38 adjacent its bottom for communication with the feed device 12. Theoutlet tube preferably is flexible and is arranged for detachment fromthe supply reservoir, for purposes described more fully hereinafter.

The constant level feed device 12 comprises a housing having anupstanding outer wall 40, a bottom wall 42 and a top wall 44. An innerwall 46 is spaced inwardly from the outer wall and is joined at itsupper end to the top wall. The inner wall extends downward andterminates a spaced distance above the bottom wall. Thus, there isprovided a feed reservoir 48 in the space between the bottom wall andthe lower end of the inner wall, and this reservoir communicates withthe annular chamber 50 formed between the outer wall and the inner wall.An outlet opening 52 communicates said annular chamber with theatmosphere.

The inner wall 46 defines an inlet chamber 54 which communicates at thelower open end of the inner wall with the feed reservoir 48. An outletopening 56 communicates this inlet chamber with the atmosphere. Theinlet chamber also communicates at its upper end with the lower end ofthe outlet tube 38 from the lower end of the supply reservorr.

The lower end of the outlet tube 38 is provided with a valve seat 58which conforms to the shape of the valve head 60 provided at the upperend of the valve member 62. The valve member is received freely withinthe inlet chamber 54 for vertical movement within the inner wall 46 andits lower end projects into the feed reservoir 48. The valve member ismade of a material which is of less density than the mercury. In thepreferred embodiment, the valve member is made of a length of hollowglass tubing closed at its bottom end and sealed at its upper end by thevalve head 60.

In the operation of the constant level feed device 12, mercury flows bygravity from the supply reservoir 10 downward through the outlet tube 38and inlet chamber 54 into the feed reservoir 48. As the level of mercuryin the feed reservoir rises, the valve member 62 also rises with ituntil the mercury reaches a level 64 at which the valve head 60 sealsagainst the valve seat 58 and thus shuts off further flow of mercuryfrom the supply reservorr.

An outfeed tube 66 communicates at its bottom end with the bottom of thefeed reservoir 48 and extends upwardly therefrom for communication atits upper end with the first boiler 14 intermediate the top and bottomends of the latter.

The position of the constant level feed device 12, and hence the lengthof the outfeed tube 66, are so chosen that the differential pressurebetween atmosphere and the sub-atmospheric pressure within the boiler,causes the mercury in the outfeed tube to rise to the point where itjust feeds into the boiler. Thus, it will be understood that theposition of the constant level feed device will vary in accordance withthe barometic pressure at the site of operation of the distillationapparatus. In this regard the constant level feed device may be mountedfor vertical adjustment on a support and the tubes 38 and 66 may beprovided as flexible tubings. Alternatively, the correct position of theconstant level feed device may be ascertained for a fixed installation,and the tubes 38 and 66 then cut to proper size, if glass or other rigidtubing is employed.

Each of the three boilers illustrated comprises a hollow housing havingan upstanding peripheral wall 68 and an annular bottom wall 70 joinedthereto. The bottom wall slopes to one side of the boiler, and a drainconduit 72 communicates through the lowermost portion of said bottomwall with the interior of the boiler. A shut-off valve 74 in each drainconduit controls communication of the latter with a common drain tube76.

Joined to the inner edge of the annular bottom wall 70 and extendingupwardly therefrom into the boiler is an inner peripheral wall 78 whichis closed at its upper end by the top wall 80. Thus, there is formed adownwardly open wall 82 centrally of each boiler for the removablereception of an electrical heater element, for heating mercury thereinto its boiling point.

The upper end of each boiler housing wall 68 is open and is joined tothe lower end of an elongated, upwardly extending condensing tube 84.The upper end of the tube is open from communication with the condensingchamber in which the tube is contained. In the preferred embodiment bestillustrated in FIG. 2, the upper end of the tube is formed in the shapeof a bowl 86 which is open at its upper end and is provided with aplurality of circumferentially spaced lateral openings 88 adjacent theupper end. A mantle 90 is mounted over this open upper end of the tube,being secured thereto by welding or otherwise joining thecircumferentially spaced downwardly projecting fingers 92 to the upperedge of the bowl. The mantle diverges downward in outwardly spacedrelation to the bowl, to direct mercury vapors from the upper end of thetube downward toward the bottom end of the condensing chamber, i.e. inthe direction opposite the source of vacuum.

Each of the condensers is formed by a hollow tube 94 defining acondensing chamber 96 therein. Each tube 94 is sealed at its bottom endto the lower, flared end of the associated condensing tube 84. In thepreferred embodiment illustrated, this joining seal is provided in suchmanner that the bottom end of the condensing chamber slopes downward tothe side which communicates with the distillate outlet tube. Thisarrangement insures complete removal of mercury distillate from thecondensing chambers.

The upper end of each condensing chamber tube is connected to a commonsource of vacuum. In the preferred embodiment illustrated, the upper endof each tube communicates with a hollow bowl 98. An inlet conduit 100from the vacuum source projects into the bowl of the first condenserassembly 14' and terminates in an upwardly directed opening 102. Aconnecting conduit 106 terminates at one end in said bowl in adownwardly directed opening 108 and terminates at its opposite endwithin the bowl of the second condensing unit 16 in an upwardly directedopening 110. A second connecting conduit 112 terminates within said bowlin a downwardly directed opening 114 and at its opposite end in anupwardly directed opening 116 within the bowl of the third condensingunit 18. The conduit 120 from the receiver flask 32 terminates withinsaid bowl in a downwardly directed opening 122.

It is by virtue of the oppositely directed openings within the bowls 98associated with the condensing units, that mercury vapor is preventedfrom being drawn into the vacuum supply. In this regard the connectingconduits 106 and 108 are arranged to slope downward toward the precedingcondensing unit so that any mercury vapor which might enter theseconduits will condense and be returned to the next preceding condensingunit.

The tube 94 defining each condensing chamber 96 is enclosed in anoutwardly spaced wall 124 which is sealed to the tube at its top andbottom ends. There is thus formed between the tube and outer wall anannular space 126 for the circulation of coolant liquid. In this regarda coolant inlet tube 128 communicates with the bottom end of the space126 associated with the first condensing unit 14', the connecting tube130' communicates the upper end of said space with the lower end of thespace associated with the second condensing unit 16, the connecting tube132 communicates the upper end of said space with the lower end of thespace associated with the third condensing unit 18, and the outlet tube134 communicates the upper end of said space with a drain.

Since maximum vaporization of mercury occurs in the first boiler 14,additional condensing surface preferably is provided in the associatedcondensing unit 14'. In the embodiment illustrated, this additionalcondensing surface is provided by the multiple hollow bowls 136positioned within the condensing chamber 96 above the condensing tubemantle and communicating at its opposite ends with the coolant space126.

Interposed between the coolant inlet tube 128 and the source of coolant,such as water, is an electric switch 138 (FIG. 3) which is actuated toclosed position when coolant is being circulated through the condensingunits. The purpose of this switch is explained in detail hereinafter,and it may be of any conventional type such as the well known fluidpressure operated diaphragm actuated switch illustrated schematically inFIG. 1.

Automatic control of operation of the apparatus is achieved by utilizingthe electrical conductivity of mercury in the various units of theassembly, in association with the electrical circuitry illustrated inFIG. 3, as follows:

In preparation for operation of the apparatus, the terminals L L and Lare connected to a suitable source of electric supply. In this regard itis to be understood that the terminal L represents a common ground towhich all of the ground connections indicated in FIG. 3 are connected.When coolant water is admitted from a tap to flow through the spaces 126of the condensing units, the electric switch 138 is closed, therebyenergizing relay 140 and effecting transfer of its associated contactfrom the position indicated and completing the electric circuit of theprimary winding of the transformer 142 associated with the rectifierpower supply 144.

Mercury to be distilled then is filled into the supply reservoir 10.When the level of mercury rises to the level of the electrical contact146 positioned adjacent the bottom of the reservoir (and insulatedelectrically therefrom), the electric circuit of the relay 148 iscompleted from the power supply 144, through said relay and contact 146,thence through the mercury to the common ground of the grounded housing34 of the supply reservoir. Contact A of relay 148 thereupon transfersfrom the closed position illustrated, to open the electric circuit ofthe neon lamp 150 which previously was energized to indicate that thesupply reservoir was empty.

When the level of mercury in the supply reservoir reaches the electricalcontact 152 positioned adjacent the top of the reservoir, the electriccircuit of the neon lamp 154 is completed, to give visible indicationthat the supply reservoir is full.

Mercury to be distilled flows by gravity from the supply reservoirthrough the tube 38 and inlet chamber 54 into the constant level feedreservoir 48 until it reaches the level 64 at which the valve member 62elevates the valve head 60 into sealing engegement with the seat 58. Thesupply of mercury from the reservoir 10 thus is shut oif.

With the source of vacuum connected to the conduit 100, the assembly ofboilers, condensers, and receiving flask are evacuated (the shut offvalves 74 being closed). Accordingly, mercury from the reservoir 48 isforced upward through the outfeed tube 66 and into the first boiler 14.As the level 64 of mercury in the feed reservoir 48 drops slightly, forexample about two millimeters, the valve member 62 drops to open thevalve and admit more mercury from reservoir 10 to restore the level 64.

When the mercury in the first boiler rises to the level of the inlet oftube 66, it interconnects electrically the electrical contact 156 whichprojects into the tube 66 and the electrical contact 158 which projectsinto the first boiler below the inlet level of the tube 66. Thiscompletes the electric circuit of the relay 160, through the closedcontact B of activated relay 148.

If desired, the contact 156 may be positioned in the boiler 14 justabove the inlet of tube 66, where it will be connected electrically tocontact 158 through the electrically conducting mercury in the boiler.

Activation of relay 160 effects transfer of its associ ated contacts Aand B from the open positions illustrated.

The manual start switch 162 then is closed momentarily to complete anelectric circuit from the power supply 144 through said switch 162 andthe normally closed contact B of inactivated relay 164, thence throughrelay 166 to the common ground. Activation of relay 166 transfers itsassociated contacts from the position illustrated, closure of contact Cforming a holding circuit for said relay to permit release of the manualstart switch.

Closure of contact A of relay 166 completes the electric circuit fromterminal L through said contact and the closed contact B of activatedrelay 160, through the electric heater element 168 associated with thefirst boiler 14, thence through the adjustable heater controltransformer 170 and the closed contact A of activated relay 160 toterminal L The heater thus is activated to heat the mercury in the firstboiler to its boiling point. The neon lamp 168 in parallel with heater168 also is activated with the latter to give visible indication thatthe first boiler is in operation.

Closure of contact B of activated relay 166 completes the electriccircuit of the neon lamp 172 to provide visible indication that thefirst boiler 14 is in automatic operation.

Simultaneously with the momentary closing of the manual start switch162, a second manual start switch 162' (coupled mechanically thereto asindicated by the dash line) also closes to complete the electric circuitfrom the power supply 144 through said switch 162 and the normallyclosed contact B of inactivated relay 174, thence through relay 176 tothe common ground. Activation of this relay 176 transfers its associatedcontacts from the positions illustrated, contact C forming a holdingcircuit therefor, and closure of contact B completes the electriccircuit of the neon lamp 178 to indicate that the second boiler 16 isready for automatic operation.

Mercury is vaporized in the first boiler 14 and condensed in theassociated condensing chamber 14' where upon it passes into the secondboiler 16. When the mercury in the second boiler rises to the level ofthe electrical contact 180 located therein above the inlet level fromthe vapor trap 22, the mercury connects said contact 180 electrically tothe contact 182 located in the second boiler below the contact 180.There is thus completed an electric circuit from the power supply 144through the relay 164 and the mercury-bridged contacts 180 and 182,thence through the relay 184 and the resistance 186 to the commonground.

Activation of relay 164 transfers its associated contacts from thepositions illustrated, the opening of contact B elfecting deactivationof relay 166 and the closing of contact A forming a bypass for the nowopened contact A of inactivated relay 166, to maintain energized theheater 168 associated with the first boiler 14.

Activation of relay 184 and the consequent transfer of its associatedcontacts A and B from the positions illustrated, completes an electriccircuit from terminal L through the closed contact A of activated relay176 and the closed contact B of activated relay 184, thence through theelectric heater element 188 associated with the second boiler 16,through the adjustable heater control transformer 1-90 and the closedcontact A of activated relay 184 to terminal L The neon lamp 188' inparallel with the heater element 188 also is energized to give visibleindication that the second boiler is in operation.

In the event the volume of mercury distillate from the first boiler 14is greater than the volume of mercury distillate from the second boiler16, the level of mercury in the second boiler ultimately will rise tothe level of the electrical contact 192 positioned above the contact180. When this occurs, the mercury will have interconnected saidcontacts electrically, thus creating an electrical shunt across therelay 164. The latter thus becomes deenergized, returning its associatedcontacts to the positions illustrated. Thus, with the opening of itsassociated contact A the electrical circuit of the heater 168 for thefirst boiler 14 is broken, as evidenced by deactivation of theassociated neon lamp 168'. The heater 168 thus is deenergized to preventfurther distillation of mercury to the second boiler, until the level ofmercury in the second boiler drops below the contact 192. When thisoccurs, relay 164 again becomes activated and the closure of itsassociated contact A completes the electric circuit of the heater 168 inthe first boiler.

In similar manner, when sufficient mercury has distilled over into thethird boiler 18 to electrically interconnect the contacts 194 and 196the electrical circuit from the power supply 144 is completed throughthe relay 174 and said contacts, thence through the relay 198 and theresistance 200 to the common ground. Activation of relay 174 causestransfer of its associated contacts, the opening of contact Bdeenergizing relay 176 and the closing of contact A maintaining therecord boiler heater 188 activated.

Activation of relay 198 and consequent transfer of its associatedcontacts from the open positions illustrated, completes the electriccircuit from terminal L through the normally closed contact A of relay202 and the closed contact B of activated relay 198, thence through theelectric heater element 204 associated with the third boiler 18, throughthe adjustable heater control transformer 206 and the closed contact Aof activated relay 198 to the terminal L Activation of the neon lamp204' gives visible indication that the third boiler is in operation.

If the volume of distillate from the second boiler 16 exceeds the outputof the third boiler 18, mercury in the latter ultimately will rise tothe level of the contact 208, thereby shunting the relay 174 and openingits associated contact A to deactivate the heater 188 in the secondboiler 16 until such time as the mercury in the third boiler drops to alevel below the contact 208.

The triple distilled mercury leaving the third condenser unit 18 throughthe outlet tube 28 is deposited in the receiver flask 32. As the levelreaches the electrical contact 210 adjacent the bottom of the flask, itcompletes the electric circuit from the power supply 144 through therelay 212, thence through the contact 210 and the mercury to the commonground of the grounded flask. Activation of relay 212 results in theopening of its associated contact and consequent deactivation of theneon lamp 214 which previously had been activated to indicate that thereceiver flask was empty.

When the mercury in the received flask rises to the level of theelectrical contact 216 positioned adjacent the top of the flask, itcompletes the electric circuit of the relay 202. Transfer of theassociated contact B from the relay 174 will be deactivated and itsassociated contact A will open to deenergize the heater element 188 inthe second boiler. In similar manner, further distillation of mercuryfrom the first boiler 14 will cease when the level of mercury in thesecond boiler 16 reaches the contact 192.

Cleaning of the components of the apparatus may be accomplished withdisassembly. Preparatory to cleaning, the outlet tube 38 is disconnectedfrom the supply reservoir 10 and the tube 100 is disconnected from thesource of vacuum. The drain valves 74, as well as the drain valves 48and 32 at the bottom of the feed reservoir 48 and receiver flask 32,respectively, then are opened to drain all of the mercury from thesystem. Thereafter the drain valves are closed, the atmosphere openings52 and 56 and the open end of the vacuum tube 100 are plugged, and thesource of vacuum is connected to the top of the receiver flask 32through the valve connection 32". The source of coolant water is shutoff, thereby opening switch 138.

Acid or other cleaning solution then is drawn in from a supply throughthe tube 38, to completely fill the feed device 12, flask 32, boilersand condensing chambers 96, completely to the bowls 98. The vacuumsource then is disconnected, by closing valve 32", to retain thecleaning solution in the assembly. After the solution has remained inthe system for a predetermined time, suitably about ten minutes, thedrain valves are opened to drain the solution from the system.

The foregoing operation is repeated a number of times with water, toflush the system, then with a volatile solvent such as alcohol, acetoneor other suitable liquid to remove all traces of water. Thereafter dryair is pumped through the system to assist in the removal of thesolvent. Finally, the system is evacuated, by again opening valve 32",and heated to insure complete vaporization of the solvent, the latterbeing removed through the vacuum system.

For the purposes of heating the system, the assembly of feed device 12and distilling units is contained within an oven which is capable ofbeing heated by the electric heater element 220. This heater element isconnected across the terminals L and L releasably through the contactsof the relays 222 and 224. The electrical circuit for relay 222 extendsfrom the common ground through said relay, thence through a thermostatswitch 226 controlled by the thermostat in the oven, thence through themanual on-off switch 228 and the normally closed contact of relay 140(when the latter is deenergized), to the terminal L Thus, it will beapparent that the heater element 220 cannot be activated until thesource of coolant liquid for the condensing units is shut off and thecoolant controlled switch 138 is opened to deenergized the relay 140.

The neon lamp 230 in parallel with the relay 222 is activated with thelatter to give visible indication that the heater element 220 isactivated.

Relay 224 is in an electric circuit which extends from a common groundthrough said relay and the thermostat controlled switch 232 controlledby a second thermostat in the oven, thence through the contact of relay140* to terminal L The switch 232 and associated relay 224 serves merelyas a safety in the event of malfunction of the primary thermostat switch226 and its associated relay 222. The primary thermostat switch 226 isset to open when the oven reaches a predetermined elevated temperature,and the thermostat switch 232 is set to open at a slightly highertemperature.

The receiver flask 32 is contained within a second oven capable of beingheated by the electric heater element 234. In manner similar to theheater element 220, the element 234 is connected across the terminals Land L releasably through the contacts of the relays 236 and 238. Theelectrical circuit for relay 236 extends from the common ground throughsaid relay and the primary thermostat control-led switch 240, thencethrough the manual on-off switch 242 and the contact of relay 140, toterminal L The neon lamp 244, in parallel with relay 236, is activatedwith the latter to give visible indication that the heater element 234is activated.

The electric circuit for the safety relay 238 extends from the commonground through said relay and the safety thermostat controlled switch246, through the contact of relay to terminal L It will be appreciatedfrom the foregoing that the present invention provides mercurydistillation apparatus Which is of simplified and compact construction,utilizing a minimum of space, provides for the continuous distillationof mercury under conditions controlled automatically by predeterminedlevels of mercury in the various components of the system, and iscapable of being cleaned with speed and facility and without disassemblyof the components.

It will be apparent to those skilled in the art that various changes maybe made in the details of construction, the numbers and arrangements ofparts, and the electrical circuitry, without departing from the spiritof this invention and the scope of the appended claims.

Having now described our invention and the manner in which it may beused, what we claim as new and desire to secure by Letters Patent is:

1. Mercury distillation apparatus, comprising (a) a mercury supplyreservoir,

(b) a plurality of distilling units each having a boiler and acondenser,

(c) outfeed means communicating the supply reservoir with the firstboiler,

(d) conduit means communicating each condenser with the next succeedingboiler,

(e) a distillate container,

(-f) conduit means communicating the last condenser with the distillatecontainer,

(g) conduit means communicating the distillate container and distillingunits with a source of vacuum,

(h) an electric heater associated with each boiler and having anelectric circuit, and

(i) electric control means in the electric circuit of each heater, eachcontrol means having an electric circuit,

(j) a pair of vertically spaced electrical contact means associated witheach boiler and arranged in the electric circuit of the control meansfor the heater of said boiler, said contact means being operable uponthe attainment of a predetermined minimum level of mercury in the boilerto be interconnected electrically by the mercury in the boiler, wherebyto 0perate the heater control means to activate the heater of saidboiler, and

(k) a pair of vertically spaced electrical contact means in each boilersucceeding the first and arranged in the electric circuit of the controlmeans for the heater of the next preceding boiler, said contact meansbeing operable upon the attainment of a predetermined maximum level ofmercury in the boiler to be interconnected electrically by the mercuryin the boiler, whereby to operate the heater control means to inactivatethe heater of the next preceding boiler.

2. The apparatus of claim 1 wherein the outfeed means includes (a) afeed reservoir having an upper annular portion and provided with anupwardly converging conical top, the top and annular portion havingatmospherecommunicating openings therethrough,

(b) infeed conduit means communicating the supply reservoir with thefeed reservoir through an opening in the apex of said conical top,

(c) a float member extending through the annular portion of the feedreservoir and having valve means .at its upper end for releasablysealing the apex opening of the conical top, the float member extendinginto the bottom portion of the feed reservoir for floating upon mercurycontained therein and to close the valve means upon attainment of apredetermined elevated level of mercury in the feed reservoir whereby tomaintain a substantially constant level of mercury in the feedreservoir, and

(d) outfeed conduit means communicating the feed reservoir with thefirst boiler.

3. The apparatus of claim 1 wherein the condensers includeinterconnected coolant liquid passages arranged to receive a coolantliquid therethrough, and the apparatus includes an electric switch inthe elect-ric circuits of the heater control means, the switch having anoperator disposed to intercept the path of coolant liquid travel andbeing operable by the passage of coolant liquid through the condenserpassages to enable operation of the heater control means to activate theheaters.

4. Mercury distillation apparatus, comprising (a) a mercury supplyreservoir,

(b) a feed reservoir,

(c) infeed conduit means communicating the top of the feed reservoirWith the mercury supply reservoir,

(d) valve means adjacent the top of the feed reservoir adapted toreleasably close the infeed conduit means from the feed reservoir,

(e) the valve means including a float member extending into the feedreservoir for engagement with mercury contained therein, the floatmember being operable to float upon the mercury and to close the valvemeans upon attainment of .a predetermined elevated level of mercury inthe feed reservoir,

(f) a plurality of distilling units each having a boiler and acondenser,

(g) outfeed conduit means communicating the bottom of the feed reservoirwith the first boiler for feeding mercury from the reservoir to saidboiler,

(h) conduit means communicating each condenser with the next succeedingboiler,

(i) a distillate container,

(j) conduit means communicating the last condenser with the distillatecontainer,

(k) conduit means communicating the distillate container and condenserswith a source of vacuum,

(I) .an electric heater associated with each boiler and having anelectric circuit,

(In) electric control means in the electric circuit of each heater eachcontrol means having an electric circuit,

(11) a pair of vertically spaced electrical contact means associatedwith each boiler and arranged in the electric circuit of the controlmeans for the heater of said boiler, said contact means being operableupon the attainment of a predetermined minimum level of mercury in theboiler to be interconnected electrically by the mercury in the boiler,whereby to operate the heater control means to activate the heater ofsaid boiler,

(o) a pair of vertically spaced electrical contact means in each boilersucceeding the first and arranged in the electric circuit of the controlmeans for the heater of the next preceding boiler, said contact meansbeing operable upon the attainment of a predetermined maximum level ofmercury in the boiler to be interconnected electrically by the mercuryin the boiler, whereby to operate the heater control means to inactivatethe heater of the next preceding boiler,

(p) the condensers including interconnected coolant liquid passagesarranged to receive a coolant liquid therethrough, and

(q) switch means in the electric circuits of the heater control means,the switch having an operator disposed to intercept the path of coolantliquid travel and being operable by the passage of coolant liquidthrough the condenser passages to enable operation of the heater controlmeans to activate the heaters.

5. The apparatus of claim 4 including a pair of vertically spacedelectrical contact means in the distillate container and arranged in theelectric circuit of the electric control means for the heater of thelast boiler, said contact means being operable upon the attainment of apredetermined maximum level of mercury in the distillate container to beinterconnected electrically by the mercuny therein, whereby to operatethe heater control means to inactivate the heater of the last boiler.

-6. Mercury distillation apparatus, comprising (a) a mercury supplyreservoir,

(b) a plurality of distilling units each having a boiler and acondenser,

(c) outfeed means communicating the supply reservoir with the firstboiler,

(d) conduit means communicating each condenser with the next succeedingboiler,

(e) a distillate container,

(f) conduit means communicating the last condenser with the distillatecontainer,

(g) conduit means communicating the distillate container and distillingunits with a source of vacuum,

(h) an electric heater associated with each boiler and having anelectric circuit,

(i) electrical safety control means in the electric circuit of eachheater and operable upon the attainment of a predetermined maximum levelof mercury in the boilers succeeding the first to deactivate the heaterassociated with the next preceding boiler,

(j) the condensers including interconnected coolant liquid passagesarranged to receive a coolant liquid therethrough, and

(k) an electric switch in the electric circuits of the heater controlmeans, the switch having an operator disposed to intercept the path ofcoolant liquid travel and being operable by the passage of coolantliquid through the condenser passages to enable operation of the heatercontrol means to activate the heaters.

References Cited UNITED STATES PATENTS 891,264 6/1908 Knipp 202-295 X2,399,334 4/ 1946 Douslin 202-160 2,450,098 9/ 1948 Smith 202-2062,547,970 4/1951 Phillips 196-132 2,598,036 5/1952 Cahill 202-1812,642,386 6/1953 Piros 203- X 2,894,680 7/1959 Hiesinger 230-401 OTHERREFERENCES Carlsen and Borchardt: A Complete Mercury PurificationSystem, Feb. 15, 1938, Industrial and Engineering Chemistry, Analyticaledition, v. 10, pp. 14-96.

Wheeler, E. L.: Apparatus for Triple Distillation of Mercury, AnalyticalChemistry, vol. 24, pp. 751-752,

NORMAN YUDKOFF, Primary Examiner. J. DONIHEE, D. EDWARDS, AssistantExaminers.

1. MERCURY DISTILLATION APPARATUS, COMPRISING (A) A MERCURY SUPPLYRESERVIOR, (B) A PLURALITY OF DISTILLING UNITS EACH HAVING A BOILER ANDA CONDENSER, (C) OUTFEED MEANS COMMUNICATING THE SUPPLY RESERVOIR WITHTHE FIRST BOILER, (D) CONDUIT MEANS COMMUNICATING EACH CONDENSER WITHTHE NEXT SUCEEDING BOILER, (E) A DISTILLATE CONTAINER, (F) CONDUIT MEANSCOMMUNICATING THE LAST CONDENSER WITH THE DISTILLATE CONTAINER, (G)CONDUIT MEANS COMMUNICATING THE DISTILLATE CONTAINER AND DISTILLINGUNITS WITH A SOURCE OF VACUUM, (H) AN ELECTRIC HEATER ASSOCIATED WITHEACH BOILER AND HAVING AN ELECTRIC CIRCUIT, AND (I) ELECTRIC CONTROLMEANS IN THE ELECTRIC CIRCUIT OF EACH HEATER, EACH CONROL MEANS HAVINGAN ELECTRIC CIRCUIT, (J) A PAIR OF VERTICALLY SPACED ELECTRICAL CONTACTMEANS ASSOCIATED WITH EACH BOILER AND ARRANGED IN THE ELECTRIC CIRCUITOF THE CONTROL MEANS FOR THE HEATER OF SAID BOILER, SAID CONTACT MEANSBEING OPERABLE UPON THE ATTAINMENT OF A PREDETERMINED MINIMUM LEVEL OFMERCURY IN THE BOILER TO BE INTERCONNECTED ELECTRICALLY BY THE MERCURYIN THE BOILER, WHEREBY TO OPERATE THE HEATER CONTROL MEANS TO ACTIVATETHE HEATER OF SAID BOILER, AND (K) A PAIR OF VERTICALLY SPACEDELECTRICAL CONTACT MEANS IN EACH BOILER SUCCEEDING THE FIRST ANDARRANGED IN THE ELECTRIC CIRCUIT OF THE CONTROL MEANS FOR THE HEATER OFTHE NEXT PRECEDING BOILER, SAID CONTACT MEANS BEING OPERABLE UPON THEATTAINMENT OF A PREDETERMINED MAXIMUM LEVEL OF MERCURY IN THE BOILER TOBE INTERCONNECTED ELECTRICALLY BY THE MERCURY IN THE BOILER, WHEREBY TOOPERATE THE HEATER CONTROL MEANS TO INACTIVATE THE HEATER TO THE NEXTPRECEDING BOILER.